I wonder if this means that the feds will stop raiding the medical mj stores on the coast (in WA)? They have been pretty busy lately.

Tough to say. The memo says that it's a "low priority" but not necessarily that they won't enforce things from time to time. Hopefully if they do go after anyone, it'll be the ones that clearly violate their list of priorities:

• Preventing marijuana distribution to minors

• Preventing money from sales from going to criminal groups

• Preventing the diversion of marijuana from states where it is legal to states where it is illegal

• Preventing criminal groups from using state laws as cover for trafficking of other illegal drugs